1. Field of the Invention
The present invention relates to a method for producing a frosted glass product, where a glass-made packaging container such as glass bottle, a glass-made table service (tableware) such as cups and dishes, or a glass-made decoration is subjected to a frost processing to form a delustered surface.
2. Description of the Related Art
The frost processing for working the surface of a glass product into a fog-like delustered surface is roughly classified into a chemical method and a mechanical method. Of these, the chemical method is called chemical frosting (or chemical frost processing) and representative examples thereof include (1) a method of mixing a hydrofluoric acid, a fluorine compound or an acid, non-uniformly corroding the glass surface to generate fine recessed faces, and thereby forming a frosted surface. On the other hand, representative examples of the mechanical method include (2) a method called sand blasting (or sand blast processing) of blowing Al2O3 (called xe2x80x9calundumxe2x80x9d), SiC (called xe2x80x9ccarborundumxe2x80x9d) or quartz sand to roughen the surface. Other examples include (3) a method of mixing silica powder or the like with a heat-curable resin or a photocurable resin, such as urethane resin, and coating the mixture on the surface of a glass product to obtain a frosted surface, (4) a method of coating and baking a coating material mainly comprising an alkoxy silane, and (5) a method of coating and baking a particulate silica or a metal oxide using a low melting point glass as the binder.
Among these, the method most commonly used for the production of a frosted glass product is the etching method (1) using a hydrofluoric acid, however, since a large amount of a hydrofluoric acid giving rise to the environmental pollution is dealt with, this method is not preferred for workers in view of labor safety and hygiene and a countermeasure must be taken for individual cases. The method (2) has a problem in that since the surface of the glass substrate is roughened by mechanically scratching it, coarse asperities are formed on the glass surface to give bad touch feeling. In other words, the glass product obtained by conventional sand-blast processing clearly differs from the product by the chemical frost processing in that the touch feeling is rough, to say nothing of the appearance. The method (3) of forming an organic material film is in need of improvement because the heat resistance and the surface hardness are low. The method (4) is disadvantageous in that a thick film cannot be formed and due to the use of an organic solvent, the work environment is bad. Also, the method (5) is disadvantageous in that glass powder and a solvent must be mixed for a long time in a pot mill at the time of producing a coating material and in the case of using an organic solvent, environmental pollution and bad working environment arise as problems and handling of the coating material requires great care. As such, each processing method has the above-described defects and therefore, a processing method ensuring touch feeling equal to that in the chemical frost, safe working and mildness to the environment is being demanded.
By taking account of these problems, the present invention provides a method for producing a frosted glass product, where a sand blast processing using a powder class abrasive and a brush polishing treatment are performed and thereby appearance and touch feeling equal to those of a product worked by the chemical frost processing can be attained. In particular, the present invention provides a method for producing a frosted glass product, which is safe in the work and at the same time, mild to the environment.
The invention of claim 1 is a method for producing a frosted glass product, which is a method for obtaining a glass product having a delustered surface such that the surface roughness Ra of the glass is from 0.4 to 1.2 xcexcm, the method comprising a step of sand-blasting a glass surface using an abrasive having a grain size of less than #220, and a step of brush-polishing the sand-blasted surface.
The invention of claim 2 is the method for producing a frosted glass product as described in claim 1, which comprises a step of water-washing the brush-polished surface.
The invention of claim 3 is the method for producing a frosted glass product as described in claim 1, wherein the brush-polishing treatment is performed while splashing water.
The invention of claim 4 is the method for producing a frosted glass product as described in claim 1, wherein the abrasive is Al2O3 or SiC having a grain size of #400 to #500.
The invention of claim 5 is the method for producing a frosted glass product as described in claim 2, wherein the abrasive is Al2O3 or SiC having a grain size of #400 to #500.
The invention of claim 6 is the method for producing a frosted glass product as described in claim 3, wherein the abrasive is Al2O3 or SiC having a grain size of #400 to #500.
The invention of claim 7 is the method for producing a frosted glass product as described in claim 1, wherein the brush-polishing treatment is performed by a nylon brush having mixed thereinto an abrasive having a grain size of #320 to #500.
The invention of claim 8 is the method for producing a frosted glass product as described in claim 2, wherein the brush-polishing treatment is performed by a nylon brush having mixed thereinto an abrasive having a grain size of #320 to #500.
The invention of claim 9 is the method for producing a frosted glass product as described in claim 3, wherein the brush-polishing treatment is performed by a nylon brush having mixed thereinto an abrasive having a grain size of #320 to #500.
The invention of claim 10 is the method for producing a frosted glass product as described in claim 4, wherein the brush-polishing treatment is performed by a nylon brush having mixed thereinto an abrasive having a grain size of #320 to #500.
The invention of claim 11 is the method for producing a frosted glass product as described in claim 5, wherein the brush-polishing treatment is performed by a nylon brush having mixed thereinto an abrasive having a grain size of #320 to #500.
The invention of claim 12 is the method for producing a frosted glass product as described in claim 6, wherein the brush-polishing treatment is performed by a nylon brush having mixed thereinto an abrasive having a grain size of #320 to #500.
The present invention is described in detail below.
In the present invention, the appearance and touch equal to those of a glass product worked by the chemical frost processing means a delustered surface where the glass surface roughness Ra is from 0.4 to 1.2 xcexcm. If the glass surface roughness Ra is less than 0.4 xcexcm, the transparency is excessively high and the high-grade effect is lost, whereas if it exceeds 1.2 xcexcm, appearance, touch feeling and the transfer paper printability becomes worse. The Ra of the delustered surface is most preferably from 0.5 to 0.9 xcexcm.
The construction material of the abrasive for use in the present invention may be any as long as it can render the glass surface foggy and examples thereof include ceramics and glass. With respect to the grain size, a powder class abrasive of less than #220 may be used. Al2O3 #220 generally used in the sand-blast processing gives a coarse glass surface having a surface roughness Ra of about 2.0 xcexcm. If the grain size is large, SiC and other abrasives similarly form large asperities on the surface, whereas if the grain size is small, although small asperities may be formed on the surface, the processing time is prolonged. Steel is not preferred because the processing takes a long time and even if the grain size is reduced, fine irregularities cannot be formed and a large Ra results. With the same grain size, SiC and glass bead give a larger Ra than Al2O3 and therefore, these preferably have a smaller grain size. Al2O3 and SiC having a grain size of #400 to #500 are preferred as the abrasive because an objective surface roughness Ra of 1.0 xcexcm or less is easily obtained and the processing rate is high.
The abrasives for use in the present invention have a grain size shown below.
The surface roughness Ra of about 1.0 xcexcm comparable to that in the chemical frost processing may be obtained only by the sand-blast processing (for example, sand-blast processing using an abrasive Al2O3 #400).
However, after the sand-blast processing, fine glass powder is adhering to the treated surface of a glass product and powdery feeling remains. Furthermore, a large number of fine cracks are present and whitish appearance is noticeable. Therefore, a secondary treatment is indispensable. In the present invention, the sand-blasted surface is brush-polished as the secondary treatment, whereby appearance and touch feeling comparable to those in the chemical frost processing can be obtained.
In the present invention, the brush polishing is performed by pressing the glass surface to a rotating brush but the brush-polishing treatment is not limited to this method. The construction material of the brush is not particularly limited but an abrasive-mixed nylon brush is preferred because of its high working speed.
The abrasive mixed into the nylon brush may be any as long as the grain size is as small as #240 or less, however, for slightly polishing the surface, an abrasive of #320 to #500 is preferred.
After the brush-polishing treatment, the glass surface is water washed (cleaned) and thereby fine glass powder can be completely removed. This water washing may be performed at the same time with the brush-polishing treatment, namely, the brush-polishing treatment may be performed while splashing water. The water at ordinary temperature can be used but the water at the temperature of approximately 50xc2x0 C. is preferred because of its easiness of drying the glass surface after the water washing.
The frosted glass product obtained by the present invention has small surface asperities and therefore, is advantageous in that printing with ceramic paint or organic paint and transfer paper printing can be performed and the latitude of design expands.